Is it safe to clean docker overlay2

Question

I got some docker containers running on AWS EC2  the  var lib docker overlay2 folder grows very fast in disk size   I m wondering if it is safe to delete its content  or if docker has some kind of command to free up some disk usage     UPDATE   I actually tried docker system prune -a already  which reclaimed 0Kb   Also my  docker overlay2 disk size is much larger than the output from docker system df  After reading docker documentation and BMitch s answer  I believe it is a stupid idea to touch this folder and I will try other ways to reclaim my disk space

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WARNING  DO NOT USE IN A PRODUCTION SYSTEM     df      dev xvda1      51467016 39384516   9886300  80          Ok  let s first try system prune     docker system prune --volumes        df      dev xvda1      51467016 38613596  10657220  79          Not so great  seems like it cleaned up a few megabytes  Let s go crazy now      sudo su    service docker stop    cd  var lib docker  var lib docker  rm -rf      service docker start  var lib docker  df      dev xvda1      51467016 8086924  41183892  17          Nice   Just remember that this is NOT recommended in anything but a throw-away server  At this point Docker s internal database won t be able to find any of these overlays and it may cause unintended consequences

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also had problems with rapidly growing overlay2   var lib docker overlay2 - is a folder where docker store writable layers for your container  docker system prune -a - may work only if container is stopped and removed   in my i was able to figure out what consumes space by going into overlay2 and investigating   that folder contains other hash named folders  each of those has several folders including diff folder   diff folder - contains actual difference written by a container with exact folder structure as your container  at least it was in my case - ubuntu 18      so i ve used du -hsc  var lib docker overlay2 LONGHASHHHHHHH diff tmp to figure out that  tmp inside of my container is the folder which gets polluted   so as a workaround i ve used -v  tmp container-data tmp  tmp parameter for docker run command to map inner  tmp folder to host and setup a cron on host to cleanup that folder   cron task was simple    sudo nano  etc crontab   30         root rm -rf  tmp container-data tmp   save and exit   NOTE  overlay2 is system docker folder  and they may change it structure anytime  Everything above is based on what i saw in there  Had to go in docker folder structure only because system was completely out of space and even wouldn t allow me to ssh into docker container

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Backgroud  The blame for the issue can be split between our misconfiguration of container volumes  and a problem with docker leaking  failing to release  temporary data written to these volumes  We should be mapping  either to host folders or other persistent storage claims  all of out container s temporary   logs   scratch folders where our apps write frequently and or heavily  Docker does not take responsibility for the cleanup of all automatically created so-called EmptyDirs located by default in  var lib docker overlay2   diff    Contents of these  non-persistent  folders should be purged automatically by docker after container is stopped  but apparently are not  they may be even impossible to purge from the host side if the container is still running - and it can be running for months at a time     Workaround   A workaround requires careful manual cleanup  and while already described elsewhere  you still may find some hints from my case study  which I tried to make as instructive and generalizable as possible    So what happened is the culprit app  in my case clair-scanner  managed to write over a few months hundreds of gigs of data to the  diff tmp subfolder of docker s overlay2  du -sch  var lib docker overlay2  lt long random folder name seen as bloated in df -haT gt  diff tmp  271G total   So as all those subfolders in  diff tmp were pretty self-explanatory  all were of the form clair-scanner-  and had obsolete creation dates   I stopped the associated container  docker stop clair  and carefully removed these obsolete subfolders from diff tmp  starting prudently with a single  oldest  one  and testing the impact on docker engine  which did require restart  systemctl restart docker  to reclaim disk space    rm -rf   ls -at  var lib docker overlay2  lt long random folder name seen as bloated in df -haT gt  diff tmp   grep clair-scanner   tail -1    I reclaimed hundreds of gigs of disk space without the need to re-install docker or purge its entire folders  All running containers did have to be stopped at one point  because docker daemon restart was required to reclaim disk space  so make sure first your failover containers are running correctly on an other node s   I wish though that the docker prune command could cover the obsolete  diff tmp  or even  diff    data as well  via yet another switch     It s a 3-year-old issue now  you can read its rich and colorful history on Docker forums  where a variant aimed at application logs of the above solution was proposed in 2019 and seems to have worked in several setups  https   forums docker com t some-way-to-clean-up-identify-contents-of-var-lib-docker-overlay 30604

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Docker uses  var lib docker to store your images  containers  and local named volumes  Deleting this can result in data loss and possibly stop the engine from running  The overlay2 subdirectory specifically contains the various filesystem layers for images and containers   To cleanup unused containers and images  see docker system prune  There are also options to remove volumes and even tagged images  but they aren t enabled by default due to the possibility of data loss

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DON T DO THIS IN PRODUCTION  The answer given by  ravi-luthra technically works but it has some issues   In my case  I was just trying to recover disk space  The lib docker overlay folder was taking 30GB of space and I only run a few containers regularly  Looks like docker has some issue with data leakage and some of the temporary data are not cleared when the container stops   So I went ahead and deleted all the contents of lib docker overlay folder  After that  My docker instance became un-useable  When I tried to run or build any container  It gave me this error   failed to create rwlayer  symlink    04578d9f8e428b693174c6eb9a80111c907724cc22129761ce14a4c8cb4f1d7c diff  var lib docker overlay2 l C3F33OLORAASNIYB3ZDATH2HJ7  no such file or directory   Then with some trial and error  I solved this issue by running    WARNING  This will delete all your data inside docker volumes   docker system prune --volumes -a   So It is not recommended to do such dirty clean ups unless you completely understand how the system works

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Everything in  var lib docker are filesystems of containers   If you stop all your containers and prune them  you should end up with the folder being empty   You probably don t really want that  so don t go randomly deleting stuff in there   Do not delete things in  var lib docker directly   You may get away with it sometimes  but it s inadvisable for so many reasons  Do this instead  sudo bash cd  var lib docker find   -type f   xargs du -b    sort -n  What you will see is the largest files shown at the bottom   If you want  figure out what containers those files are in  enter those containers with docker exec -ti containername --  bin sh and delete some files  You can also put docker system prune -a -f on a daily weekly cron job as long as you aren t leaving stopped containers and volumes around that you care about   It s better to figure out the reasons why it s growing  and correct them at the container level

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I had this issue    It was the log that was huge  Logs are here     var lib docker containers  lt container id gt   lt container id gt -json log   You can manage this in the run command line or in the compose file  See there   Configure logging drivers  I personally added these 3 lines to my docker-compose yml file    my container    logging      options        max-size  10m

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I recently had a similar issue  overlay2 grew bigger and bigger  But I couldn   t figure out what consumed the bulk of the space  df showed me that overlay2 was about 24GB in size  With du I tried to figure out what occupied the space    and failed  The difference came from the fact that deleted files  mostly log files in my case  where still being used by a process  Docker   Thus the file doesn   t show up with du but the space it occupies will show with df  A reboot of the host machine helped  Restarting the docker container would probably have helped already    This article on linuxquestions org helped me to figure that out

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Friends  to keep everything clean you can use de commands   docker system prune -a  amp  amp  docker volume prune

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I used  docker system prune -a  it cleaned all files under volumes and overlay2       root jasontest volumes   docker system prune -a     WARNING  This will remove              - all stopped containers             - all networks not used by at least one container             - all images without at least one container associated to them             - all build cache     Are you sure you want to continue   y N  y     Deleted Images      untagged  ubuntu 12 04     untagged  ubuntu sha256 18305429afa14ea462f810146ba44d4363ae76e4c8dfc38288cf73aa07485005     deleted  sha256 5b117edd0b767986092e9f721ba2364951b0a271f53f1f41aff9dd1861c2d4fe     deleted  sha256 8c7f3d7534c80107e3a4155989c3be30b431624c61973d142822b12b0001ece8     deleted  sha256 969d5a4e73ab4e4b89222136eeef2b09e711653b38266ef99d4e7a1f6ea984f4     deleted  sha256 871522beabc173098da87018264cf3e63481628c5080bd728b90f268793d9840     deleted  sha256 f13e8e542cae571644e2f4af25668fadfe094c0854176a725ebf4fdec7dae981     deleted  sha256 58bcc73dcf4050a4955916a0dcb7e5f9c331bf547d31e22052f1b5fa16cf63f8     untagged  osixia openldap 1 2 1     untagged  osixia openldap sha256 6ceb347feb37d421fcabd80f73e3dc6578022d59220cab717172ea69c38582ec     deleted  sha256 a562f6fd60c7ef2adbea30d6271af8058c859804b2f36c270055344739c06d64     deleted  sha256 90efa8a88d923fb1723bea8f1082d4741b588f7fbcf3359f38e8583efa53827d     deleted  sha256 8d77930b93c88d2cdfdab0880f3f0b6b8be191c23b04c61fa1a6960cbeef3fe6     deleted  sha256 dd9f76264bf3efd36f11c6231a0e1801c80d6b4ca698cd6fa2ff66dbd44c3683     deleted  sha256 00efc4fb5e8a8e3ce0cb0047e4c697646c88b68388221a6bd7aa697529267554     deleted  sha256 e64e6259fd63679a3b9ac25728f250c3afe49dbe457a1a80550b7f1ccf68458a     deleted  sha256 da7d34d626d2758a01afe816a9434e85dffbafbd96eb04b62ec69029dae9665d     deleted  sha256 b132dace06fa7e22346de5ca1ae0c2bf9acfb49fe9dbec4290a127b80380fe5a     deleted  sha256 d626a8ad97a1f9c1f2c4db3814751ada64f60aed927764a3f994fcd88363b659     untagged  centos centos7     untagged  centos sha256 2671f7a3eea36ce43609e9fe7435ade83094291055f1c96d9d1d1d7c0b986a5d     deleted  sha256 ff426288ea903fcf8d91aca97460c613348f7a27195606b45f19ae91776ca23d     deleted  sha256 e15afa4858b655f8a5da4c4a41e05b908229f6fab8543434db79207478511ff7      Total reclaimed space  533 3MB      root jasontest volumes   ls -alth     total 32K     -rw-------  1 root root  32K May 23 21 14 metadata db     drwx------  2 root root 4 0K May 23 21 14       drwx--x--x 14 root root 4 0K May 21 20 26

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I found this worked best for me   docker image prune --all   By default Docker will not remove named images  even if they are unused   This command will remove unused images   Note each layer in an image is a folder inside the  usr lib docker overlay2  folder

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adding to above comment  in which people are suggesting to prune system like clear dangling volumes  images  exit containers etc   Sometime your app become culprit  it generated too much logs in a small time and if you using empty directy volume  local volumes  this fill the  var partitions   In that case I found below command very interesting to figure out  what is consuming space on my  var partition disk  du -ahx  var lib   sort -rh   head -n 30 This command will list top 30  which is consuming most space on a single disk  Means if you are using external storage with your containers  it consumes a lot of time to run du command  This command will not count mount volumes  And is much faster  You will get the exact directories files which are consuming space  Then you can go to those directories and check which files are useful or not  if these files are required then you can move them to some persistent storage by making change in app to use persistent storage for that location or change location of that files  And for rest you can clear them

[docker] Is it safe to clean docker/overlay2/

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